Communication System Determining Effective Remaining Transmission Rate Using Small-Sized Test Data Before Transmitting Actual Data

1. A communication system for use with a communication network, said communication system comprising: a plurality of communication devices, including a processor and memory, to be connected to each other through the communication network, said plurality including at least a first communication device and a second communication device; wherein the first communication device is configured to: transmit load data between said first communication device and any other communication device among said plurality of communication devices at a plurality of difference transmission rates, measure first response times, each of the first response times indicating a length of time for transmitting test data, whose size is smaller than a size of the load data, between the first and second communication devices at one of the plurality of different transmission rates, and store a transmission rate table in a storage device, the transmission rate table including the first response times, and the transmission rates associated with the first response times, respectively, and wherein, the first communication device is configured to, when transmitting actual data from the first communication device to the second communication device: determine a necessary transmission rate for transmitting the actual data; detect a second response time indicating a length of time for transmitting the test data between the first and second communication devices; determine a transmission rate associated with the second response time, as a used transmission rate, based on the transmission rate table; determine an effective remaining transmission rate of the communication network available to transmit the actual data, based on a maximum transmission rate of the communication network and the used transmission rate, the effective remaining transmission rate being a transmission rate indicating an amount of additional data which can be transmitted over the communication network where traffic is occurring; and start transmission of the actual data when the effective remaining transmission rate is higher than the necessary transmission rate.

2. The communication system as claimed in claim 1 , wherein the first communication device is configured to obtain the maximum transmission rate, wherein the first and second communication devices are configured to start an exclusive-use state where only the first and second communication devices communicate with each other over the communication network, and wherein the first communication device is configured to, in the exclusive-use state: measure the first response times by transmitting the test data between the first and second communication devices, while transmitting the load data at the plurality of different transmission rates between the first and second communication devices; and store the first response times, and the transmission rates of the load data associated with the first response times, in the transmission rate table.

3. The communication system as claimed in claim 1 , wherein said plurality of communication devices further comprises a third communication device and a fourth communication device, wherein the first communication device is configured to obtain the maximum transmission rate, wherein the first communication device, the second communication device, the third communication device, and the fourth communication device are configured to start an exclusive-use state where only the first communication device, the second communication device, the third communication device, and the fourth communication device communicate with each other over the communication network, and wherein the first communication device is configured to, in the exclusive-use state: measure the first response times by transmitting the test data between the first and second communication devices, while transmitting the load data at the plurality of different transmission rates between the third and fourth communication devices; and store the first response times, and the transmission rates of the load data associated with the first response times, in the transmission rate table.

4. The communication system as claimed in claim 2 , wherein the first and second communication devices are configured to start an exclusive-use state where only the first and second communication devices communicate with each other over the communication network, and wherein the first communication device is configured to measure the maximum transmission rate by transmitting load data between the first and second communication devices.

5. The communication system as claimed in claim 3 , wherein the third and fourth communication devices are configured to start an exclusive-use state where only the third and fourth communication devices communicate with each other over the communication network, wherein the third communication device is configured to measure the maximum transmission rate by transmitting load data between the third and fourth communication devices, and wherein the first communication device is configured to obtain the maximum transmission rate from the third communication device.

6. The communication system as claimed in claim 3 , wherein the first and second communication devices are configured to start an exclusive-use state where only the first and second communication devices communicate with each other over the communication network, wherein the first communication device is configured to measure the maximum transmission rate by transmitting load data between the first and second communication devices, wherein the third and fourth communication devices are configured to start an exclusive-use state where only the third and fourth communication devices communicate with each other over the communication network, and wherein the third communication device is configured to measure the maximum transmission rate by transmitting load data between the third and fourth communication devices.

7. The communication system as claimed in claim 2 , wherein the first communication device is configured to measure the first response times by obtaining an average length of times for transmitting the test data a plurality of times between the first and second communication devices.

8. The communication system as claimed in claim 2 , wherein the first communication device is configured to measure the first response times by obtaining a maximum length of times for transmitting the test data a plurality of times between the first and second communication devices.

9. The communication system as claimed in claim 2 , wherein the first communication device is configured to measure the first response times by obtaining a minimum length of times for transmitting the test data a plurality of times between the first and second communication devices.

10. The communication system as claimed in claim 1 , wherein the first communication device is configured to detect the second response time by obtaining an average length of times for transmitting the test data a plurality of times between the first and second communication devices.

11. The communication system as claimed in claim 1 , wherein the first communication device is configured to detect the second response time by obtaining a maximum length of times for transmitting the test data a plurality of times between the first and second communication devices.

12. The communication system as claimed in claim 1 , wherein the first communication device is configured to: compare interpolated or extrapolated values of the first response times and the transmission rates stored in the transmission rate table, with the second response time, and determine a transmission rate associated with the second response time, as the used transmission rate.

13. The communication system as claimed in claim 1 , wherein the effective remaining transmission rate is a remaining transmission rate obtained by subtracting the used transmission rate from the maximum transmission rate.

14. The communication system as claimed in claim 1 , wherein the effective remaining transmission rate is a remaining transmission rate obtained by subtracting the used transmission rate and a predetermined margin from the maximum transmission rate.

15. The communication system as claimed in claim 1 , wherein the first communication device is provided with a first indicator; and wherein the first communication device is configured to, when the effective remaining transmission rate is less than or equal to the necessary transmission rate: cancel the transmission of the actual data, and display on the first indicator, a fact that the transmission of the actual data has been cancelled.

16. The communication system as claimed in claim 15 , wherein the first communication device is configured to, after starting the transmission of the actual data: detect a third response time indicating a length of time for transmitting the test data, while transmitting the actual data between the first and second communication devices; determine a transmission rate associated with the third response time, as a used transmission rate, based on the transmission rate table; determine the effective remaining transmission rate based on the maximum transmission rate of the communication network and the used transmission rate; and display on the first indicator, a fact that the transmission of the actual data is unstable, when the effective remaining transmission rate is less than or equal to a predetermined threshold value.

17. The communication system as claimed in claim 1 , wherein the first communication device is configured to, when the effective remaining transmission rate is less than or equal to the necessary transmission rate: cancel the transmission of the actual data, and notify the second communication device of a fact that the transmission of the actual data has been cancelled, and wherein the second communication device is provided with a second indicator; and wherein the second communication device is configured to display on the second indicator, a fact that the transmission of the actual data has been cancelled.